configure dns

“…My DSL service providers DNS server seems to be little slow, they have two servers it takes little time (some time upto 2 seconds) to resolve a domain name, once domain resolved, browsing speed remains the same, what should I do to improve DNS performance?….”

The answer is use a DNS proxy i.e. Dnsmasq. It is a a lightweight, easy to configure DNS forwarder and optional DHCP server. Dnsmasq is targeted at home networks using NAT and connected to the internet via a modem, cable-modem or ADSL connection but would be a good choice for any small network where low resource use and ease of configuration are important. The main use of the DNS proxy is to increase speed. Generally all computer send their request to ISP’s DNS servers. But with DNS proxy request are cached. It stands between your local system and firewall server. Here is our sample network setup, 192.168.1.1-3 are all desktop system, 192.168.1.254 is our Linux firewall server:

Step # 2 Configure Dnsmasq

To be frank you don’t have to change a single line in /etc/dnsmasq.conf. However you need to setup 127.0.0.1 as dns server name in /etc/resolve.conf file:

# vi /etc/resolve.conf

nameserver 127.0.0.1 nameserver 202.54.10.1 nameserver 202.54.20.1

Replace 202.54.10.1/202.54.20.1 with your actual ISP DNS server IPS. The dnsmasq should read the list of ISP nameservers from the automatically /etc/resolv.conf. You should list 127.0.0.1 as the first nameserver address in /etc/resolv.conf. So local desktop clients always gets cached queries.

Step # 3 Restart/start Dnsmasq

# /etc/init.d/dnsmasq start

Step # 4 Update DNS server IPS for all desktop systems

It is easy to use Dnsmasq rather than setting up caching BIND server. But hold on it has some cool usage too. You can add domains which you want to force to specific IP address. For example, doubleclick.net displays ugly adds on many sites, just send this server it to our 127.0.0.1 (i.e. your local server ). Just open a file /etc/dnsmasq.conf and add following line to it:address=/doubleclick.net/127.0.0.1

Restart Dnsmasq and make sure you runs local webserver at 127.0.0.1 with some default page. Read the Dnsmasq man page and docs for more information.